16hg @Idle/what could it be?

[highPSI-S4]

So this has been going on or awhile now the car sits @ 15hg while idling after warm up. Since i moved and now have a garage i just bought a compressor this weekend. I decided to try and put an end to this leak or whatever it is. while pressure testing I sprayed soapy water over every hose.

1. Leaky diverters- I tightened them and there fine now
2. leak near TBB- just had to tightrn the clamp
3. Big leak in the passenger side stock intercooler.

I thought 3 was the big ticket i took the whole bumper off and see the water drip and hit the spot where it was leaking. it looked like Moby Dick's port hole blowing water. I texted a local member to about the issue and later in the week he's going to let me get he's stock one's but for the meen time i used gasket seal and bondo to cover the hole. after I let it dry I re-installed it and pressure tested again. Didn't blow any air and i couldn't hear any escape or see any soapy suds. Put the car back together and started it back up hoping for change and THE ****** IS STILL @ 15hg.........................WTF

I was thinking valve cover gaskets of maybe intake manifold were leaking but couldn't tell and 15hg @ idle would have to be a big leak, so why can't i find it?

After the car was together i warmed it up and took a test drive, and it pulls hard and the siren isn't as loud as it use to be so that made me happy a little but why 15hg.

Also I'm currently running stock intake w/ darintake mod.

Any help please, I want to go STG 3 this summer but i won't until i find out what is wrong.



Vernon

[gointoscott]

Yeah I feel your pain. Mine isnt that low. Mine is around 18hg but I wish it was at 20hg. When I'm driving and then let off the gas it goes to 20-21hg's but if it idles it will fluctuate between 18-19 hg's So not horrible but I want it to be correct. I am at full boost as well.

I found a small leak by brake booster, replaced it and thought my troubles were fixed. Nope just like you.

So yeah any other info would be good to hear. the other thing I was thinking maybe was spider hose??? Would this affect vacuum? maybe its both our problems.

[highPSI-S4]

Yeah I feel your pain. Mine isnt that low. Mine is around 18hg but I wish it was at 20hg. When I'm driving and then let off the gas it goes to 20-21hg's but if it idles it will fluctuate between 18-19 hg's So not horrible but I want it to be correct. I am at full boost as well.

I found a small leak by brake booster, replaced it and thought my troubles were fixed. Nope just like you.

So yeah any other info would be good to hear. the other thing I was thinking maybe was spider hose??? Would this affect vacuum? maybe its both our problems.

Yeah mine goes 2 20-21hg's when I let off as well, if it didn't then i'd buy a new gauge but it seems to be working fine. My spider hose was just replaced and i also had to replace my Samco f-hose, so i got the 034 one instead.

[Blue AWD]

It should be more like 22-24 when you let off the gas, I think.

[00s4slvr]

yeah actually i have a tip and when i start my car in the morning and its cold it will be in about 19-20Hg. Then when i put it in drive it goes up to about 16-17Hg when i idle, but after i drive for about 5-10 mins and then when the car is in drive at idle its at 18Hg and when its in park its at about 20-21hg. And when i let go of the gas when i am driving its about 24-25 HG.

[AAAA]

vernon your car is the devil. or maybe the devil's son--i think my car is the devil. I've done quite a bit more that has broken since we last talked, finally fixed everything--for now

[highPSI-S4]

vernon your car is the devil. or maybe the devil's son--i think my car is the devil. I've done quite a bit more that has broken since we last talked, finally fixed everything--for now

I pm'ed you scott.

[highPSI-S4]

morning bump

[AudiSportB5S4]

hmm that sucks Vernon... Did you ever take off the Y pipe and investigate around? Maybe something by the intake manifold is leaking, 16 is deff. too low.

[RolledMySTi]

You need to pressure test again. Get the y-pipe pointed up so you can spray the hosed on the back of the motor.

Other than that do you have access to a vag com to make sure there are no bad sensors?

[ThirdStrike]

boost gauges arent always correct. ive logged my boost and seen a difference of 2-3 psi.
usually a small leak wont even show up on the gauge depending on where you T'd it off of. i had 3 leaks and my gauge still read the same even after i fixed it, but i T'd off the FPR lines.
id trust the pressure test rather than the gauge

[lsc2g]

mine at idle is -18,-19 and if i accel and let off the gas -21-22

i'm pretty sure i don't have a boost leak as i can still do 15PSI full boost no problem..

but i'd like to see -20 idle too.. my old mk4 jetta always purred at -20.. ahh well

[highPSI-S4]

Yeah i VAGed the car for awhile ago, i only have a code for my rear o2's because i have some high flow cats. other than that i VAG the car every month to check on the status of the car and i never reset it and no new codes pop up.

I tryed pulling the pipe up a bit but it was starting to come out of the hoses for the inlets.
But i was able to remove the stock air box and pull the y-pipe up slighty and i was able to spray the soapy water on the wastgate hoses,and hoses connected to the intake manifold and everything else but saw nothing. My only guesses are maybe intake manifold gaskets or vavle cover gaskets- but with a leak that big why can't i find it.

[AudiSportB5S4]

that is interesting.. I would suspect the intake mani before the valve cover gaskets... wasn't your car taken apart ? maybe those bolts weren't all tightened enough, there's a lot of them in there holding the intake mani down if you've seen them before. Some are hard to get to...

[highPSI-S4]

that is interesting.. I would suspect the intake mani before the valve cover gaskets... wasn't your car taken apart ? maybe those bolts weren't all tightened enough, there's a lot of them in there holding the intake mani down if you've seen them before. Some are hard to get to...

I did check the bolts and they all seem very tight on the Manifold, that's why this is so puzzling to me.

I did have headwork done a year ago and an Audi tech did the install, I checked the work and can't seem to find anything wrong. Although i do have a burning oil smell which from previous threads meens maybe valve cover gasket is leaking. I check and i don't see any oil however i do have a dime shaped oil puddle in the garage.

On the way to work I turned the corner and went WOT and again car pulls like a freight train, but it was 25 degrees out. So i don't know maybe there isn't anything wrong.

[S4evr]

during warm up where does it sit?

[highPSI-S4]

during warm up where does it sit?

It sits @ 16hg when warm. When i first start the car it's sitting @ 14hg.

Like i said earlier, car throws no codes related to this and the car pulls very hard.

I used the T coming of the FPR for the boost reading. Maybe i should buy a new gauge and see what happens.

[Evilevo]

Vernon, you should buy my Set up and go Stage 3+!!!!

Mine doesnt idle at 20, and i had no leaks anywhere. My Evo only idled at like 15 or so, but that is cause it had cams. If there are no leaks anywhere, and the car pulls fine, than i wouldnt worry about it that much

[highPSI-S4]

Vernon, you should buy my Set up and go Stage 3+!!!!

Mine doesnt idle at 20, and i had no leaks anywhere. My Evo only idled at like 15 or so, but that is cause it had cams. If there are no leaks anywhere, and the car pulls fine, than i wouldnt worry about it that much

So tempting, but right now I have some other things on the S4 to get and I have an Engagement ring to purchase as well, that's why i said STG-3 this summer.

If you have them in another 2months or so, It would be more likely.

[sCeRaXn]

How long has this been happening? Has it idled at 20in/hg since youve had the headwork? Ive seen many cars lose some vacuum after getting headwork done, especially if there was significant work done to the exhaust side. If its idled at 15in/hg since youve gotten the headwork, and you have no other boost leaks then i wouldnt worry too much about it.

[highPSI-S4]

How long has this been happening? Has it idled at 20in/hg since youve had the headwork? Ive seen many cars lose some vacuum after getting headwork done, especially if there was significant work done to the exhaust side. If its idled at 15in/hg since youve gotten the headwork, and you have no other boost leaks then i wouldnt worry too much about it.

You know I never payed attention to what it was prior to the headwork. Yeah but the problem is i've had many boost leaks since the work was done and my vaccum has never changed, didn't matter weather i had a boost leak or fixed one.

One thing i do know, there have aleast 2-3 times i took some things apart intake related and start the car and it was @ 19-20hg and then later that day it would be back @ 15-16hg. But that doesn't happen anymore. it's always @ 15hg now. But i'am beginning to think it's fine but i want to be sure before I continue to mod the car.

[Evilevo]

So tempting, but right now I have some other things on the S4 to get and I have an Engagement ring to purchase as well, that's why i said STG-3 this summer.

If you have them in another 2months or so, It would be more likely.

If people keep on faking i just might!

[Rajan147]

http://www.onlineconversion.com/pressure.htm

its funny because, you made me paranoid talking in in/hg, so i had to go through and convert everything to bar.

[GetAwayFromMe]

At one time i forgot to plug in one of the spyder hoses and my vac was 15 at idle. I plugged it in and everything went to norman. Might want to check if the spyder hose has cracks in it. Right now my sits at 21/22 when warm and about 26 when i accel and let go.

[gointoscott]

At one time i forgot to plug in one of the spyder hoses and my vac was 15 at idle. I plugged it in and everything went to norman. Might want to check if the spyder hose has cracks in it. Right now my sits at 21/22 when warm and about 26 when i accel and let go.

I think this may be my problem. Well not that its unplugged but that its leaky. I think its hard to check the spider hose when doing leak test because you unplug the pcv part from intake when doing test or does it still get pressure from intake from the other end? Anyone know? I might order one and see if that helps my problem. My car is approaching 100k so chances are its wearing out anyway. Dang things are not cheap though.

[GetAwayFromMe]

I think this may be my problem. Well not that its unplugged but that its leaky. I think its hard to check the spider hose when doing leak test because you unplug the pcv part from intake when doing test or does it still get pressure from intake from the other end? Anyone know? I might order one and see if that helps my problem. My car is approaching 100k so chances are its wearing out anyway. Dang things are not cheap though.

You can leave it on and pressure it at maybe 5psi and see if it leaks. Spyder hose has barely any pressure so if you have a leak you will see it fast.

When you buy the new one have fun replacing it

[gointoscott]

You can leave it on and pressure it at maybe 5psi and see if it leaks. Spyder hose has barely any pressure so if you have a leak you will see it fast.

When you buy the new one have fun replacing it

I will have to try that. I thought that if you leave it connected it will push oil through and it may smoke some for a bit till the oil burns out. I suppose if you dont put much pressure and dont do it for a prolonged time it wont do that.

I take it that its kind of hard to replace? That surprises me a little because the brake booster was a piece of cake. What all is involved in replacing it? Why is it difficult?

[highPSI-S4]

I will have to try that. I thought that if you leave it connected it will push oil through and it may smoke some for a bit till the oil burns out. I suppose if you dont put much pressure and dont do it for a prolonged time it wont do that.

I take it that its kind of hard to replace? That surprises me a little because the brake booster was a piece of cake. What all is involved in replacing it? Why is it difficult?

Not sure why it's hard, looks easy to me. Either way mine was replaced about 8months ago so i know it's not bad. You've done DIY piggies so you can def. handle this job I think the spider hose assembly is like 150.00 or so.

[gointoscott]

Yeah I didnt think it'd be that hard to do either.
So you replaced yorus already and still having a problem?

One thing to think about is you need to think outside the box. maybe the spider hose was defective from new. probably not but cant rule it out.

i'm gonna pressure test mine and see if it makes a difference. Do you have your old spider hose? maybe try putting it back on and see if you notice a difference.

[highPSI-S4]

Yeah I didnt think it'd be that hard to do either.
So you replaced yorus already and still having a problem?

One thing to think about is you need to think outside the box. maybe the spider hose was defective from new. probably not but cant rule it out.

i'm gonna pressure test mine and see if it makes a difference. Do you have your old spider hose? maybe try putting it back on and see if you notice a difference.

No, I don't have my old spider hose. The Audi Tech that worked on the car replaced it. The old hose was broken in many places and was visible.

I'll try and see what i can find this weekend. But like i said the car pulls like a freight train. So

[highPSI-S4]

I also PMed a Local Audi tech about my issue's/Low Vaccum @ Idle. Just for reference this is what he wrote.

"As fas as your vacuum leak goes, its very possible that the suction jet pump or the brake vacuum pump isn't working but there are several places to lose vacuum on your motor. Pressure testing won't reveal a vacuum leak if its on a system that closes under boost. You have two sides to your intake and certain check valves close when they see pressure while others stay open all the time. If you have a vacuum leak that is only present out of boost a pressure test may not reveal it. I'd get a few cans of carb cleaner and start spraying down all of your vacuum lines and hoses. If the idle changes while your doing it then you can pinpoint the problem. Assuming its a vacuum leak that's the poor mans tester (and the easy way if you ask me)"


Now I've down the spray all hoses with carb cleaner and nothing happened, car didn't stutter or try to cut off. So if he's right about the brake hose thing being bad that could be why the reading is off.

Just thought i would share this info.

[S-Power]

A lot of knowledge and Info in this thread

Great for reference

[highPSI-S4]

Here's an UPDATE


Got another pair of intercoolers off another member and installed those, while doing so I saw alot of oil on the driver's side. Upon taken nearly the whole front end off, I found i have a very badly leaking valve cover gasket. There was oil everywhere, i didn't see it a few days ago so it must have gotten bigger but i knew i had one. I took the drivers side cover off to see the whole bottom area of the gasket(side closest to the exhaust manifold was leaking) The gasket should have been new, and i'm sure the screws were tight. After cleaning up some of the mess i reinstalled it( ordering a new one) and put the car together and it was started her up, see purred around 18hg for awhile but once she warmed up she was back to 15hg so now i'm certain this is my boost leak issue.
I'll update again once i install the new gasket, might be a couple weeks as I have other thing to do on the car as well.

[gointoscott]

Thanks for the update Keep us informed. Mine isnt leaking that bad (as far as I know so who knows maybe they are. seams to be a common problem)

I also wonder if I have some leaks in my IC's I should test them. I really would like to upgrade them. But want to stick with SMIC's.

[AudiSportB5S4]

Vernon, check your PMs !

[code7rpd]

What should the vac reading be at idle when cold and hot for a healthy motor?

[AudiSportB5S4]

What should the vac reading be at idle when cold and hot for a healthy motor?

18-19 on cold start, after warming (idling) should settle to 21.